This invention relates to a process for treating aluminum surfaces. More particularly, this invention relates to a process for treating aluminum surfaces in preparation for a plating, brazing or welding operation.
It has long been known that in order to attain an adherent coating on the surfaces of aluminum and aluminum alloy articles it is necessary to clean the surface of oxides and other foreign matter. Methods for accomplishing the requisite cleaning have been the subject of numerous patents and publications. For example, in U.S. Pat. No. 1,457,149 there was disclosed a process for cleaning such surfaces by scouring with an abrasive, preferably in the presence of water, prior to a plating operation. More recently, in U.S. Pat. No. 2,968,577, a process was disclosed which included the steps of dry polishing with an abrasive body followed by a chemical pickling of the surfaces to remove oxides and then wet polishing the surface with an abrasive prior to a coating operation. Mechanical abrasion of aluminum surfaces in a non-oxidizing atmosphere has also been employed to achieve adherent coatings in a subsequent vacuum-deposition process, as shown in U.S. Pat. No. 3,012,904. The use of a low-density abrasive article to clean metal surfaces as a step in a coating or plating operation was described in U.S. Pat. No. 3,449,176. With these and other prior art processes it was thought essential to coat or plate aluminum surfaces simultaneously with the cleaning step or immediately thereafter in order to avoid surface oxidation and a concommitant loss in adhesion of the coating or plate. When applied to continuous processes as for example in a process for plating continuous aluminum strip, it thus became necessary to design process machinery that included both cleaning and coating equipment.